Burner control system



M A H G W N N u a L L BURNER comm. sysm Shams-Sheet 1 Film 111.1%. 31. 194-6 INVEWTOR.

L. L. CUNNINGHAM BURNER CONTROL SYSTEM 1mm Aug. '31, 1946 i wow-Sheet. 2

INVENTOR.

4 Sheetw-Sheet 8 0cm 3,, mm IL. L. CUNNINGHAM BURNER con'mom. svsmw Filed Aug. 31. 1948 195 L, L. @UNMNGHAM 2,5243

511mm Comm. SYS

Filed Aug. 31, 1946 4 Sheets-Shem 4 IN V EN TOR.

Patented Oct. 3, 1950 OFFICE BURNER. CONTROL SYSTEM I iewis L. Cunningham, Sherman Oaks, Calif. Application August 31, 1948, Serial N 0. 694,372

This invention relates to improvements in heat regulating and other devices and has as a general and broad object to provide means for regulating, or modulating, the flow of fluids in proportion to the demand for such flow, such demand being determined by variation in temperature or other conditions.

A main object of the invention is to modulate, for example, gas flow to a burner in a predetermined ratio to the temperature between predetermined limits at a chosen location and to modify this ratio in such a manner as may be required to meet the pressure requirements of the burner.

It is well known that in order to maintain a relatively constant temperature in, for example, an occupied space, it is necessary to modulate, or proportion, the flow of heat to the space in accordance with the temperature changes and to avoid. in so far as is practicable, abrupt changes in the rate of flow of heat. It is also well known that gas burners, particularly of the Bunsen type, do not operate properly when the pressure of the gas supplied to them is not maintained between definite limits and, in particular, their operation isunsatisfactory when the presa can. (Cl. sac-1) sure of the gas is relatively low and, in fact, they cannot usually be lighted successfully if the pressure of the gas supplied to them at the time of lighting is not a relatively high percentage of the maximum pressure for which they are designed. If such pressure is relatively low "flashbacks" are apt to occur, in which case combustion takes place in the mixing chamber of the burner and normal combustion at the burner proper is seriously interfered with.

Features of this invention include the broad idea of modulating the pressure of the gas supplied to the burner, in response to variation of a variable such as temperature, within limits suitable for proper burner operation and when the demand for heat tends to result in a gas pressure less than is suitable for proper burner operation to abruptly shut oh the flow of gas and when the flow of gas hasthus been shut on to again supply gas pressure to the burner only when the demand is such that the corresponding pressure is great enough for the burner to light properly.

A further object of the invention is to cut oil all gas flow, both to a safety pilot and a burner, if the safety pilot light should become extinguished, and to permit the safety pilot to be lighted without the possibility of gas being supplied to the main burner until the safety pilot light is in normal operating condition.

A further object of the novel and useful means for temporarily interrupting flow of gas to the main burner if a flashback, above referred to, should occur either at lighting or durin otherwise normal operation and to restore normal operation if the burner can be lighted without a flashback occurring.

Reference is now made to the drawing in which:

Figure 1 illustrates an embodiment of the invention.

Figure 2 is a cross-section view indicated by 2-2 in Figure 1 of a portion oi the apparatus shown in Fig. 1.

Figure 3 is a fragmentary, sectional view taken along the line 3-3 in Figure 2.

Figure 4 is a fragmentary, sectional view taken along the line 4-4 in Figure 3.

Figure 5 is a fragmentary, sectional view along the line 55 in Figure 3.

Figure 6 is a view partially in section, of a combination safety pilot and bleed gas burner taken which constitutes a part of the invention.

Figure 7 is a fragmentary, sectional view. taken along the line 1-1 of Figure 6. l I

Figure 8 is a sectional view taken along the line 8-8 of Figure 6.

Figure 9 is a fragmentary, sectional view taken along the line 8-9 of Figure 8 showing the construction of the safety pilot shut-oil valve and the air-gas mixer 01 the safety pilot.

Figure 10 is a detail view, partially in section of the shut-oil valve shown in Figure 9.

Figure 11 is a diagrammatic illustration of the apparatus shown in Figure 1.

Figure 12 is a diagrammatic. illustration of system connections for multiple burner operation.

The operation of the invention may now be described:

Gas from a suitable source is supplied at I to the space 2 of the regulating valve, Fig. 2. The

valve member 3, urged toward closure by the' spring 4 acting through a suitable member 5, normally prevents passage of gas into the space 6, conduit 1 and burner 8 which in Fig. 1 is illustrated as a raw gas, or luminous type, burner while in Fig. 11 a Bunsen type burner is illustrated, the invention being adaptable for use with either type.

Gas under suitable pressure in the space 2 passes through the opening 9 to the conduit II and thus to the space I I of the safety pilot shown generally in Fig. 6 and Fig. 9. If the valve I! (Fig. 9) is open, which it is for normal operation, it can only be open to the extent permitted by the adjustable stop means l3 so that a relainvention is to provide I tively small movement of the valve I2 away from the stop I3 will result in complete closure. However, the valve I2 being normally open, gas passes into the space I4 and thence to the burner of the safety pilot and to other means to be described I later;

The valve I2, shown in detail in Figure 10, embodies a suitable stem centrally drilled and slotted as shown at I5 so that the plug I3, when forced into the somewhat smaller central drilling spreads the prongs I1 of the valve stem as shown. The sleeve I3, having a close but slidable fit in the retainer plug I9 is internally drilled at 23 as shown so that the prongs I1 must be compressed radially to be inserted into the drilled hole 23. The resulting frictional engagement of the prongs I1 with the sleeve I8 tends to cause the valve I2 to follow any motion of the sleeve I3 but upon restraint of motion of the valve I2 the sleeve I8 may move with reference to the valve I2.

Referring to Fig. 9 the slots I5 in the stem of the valve I2 permit passage of gas from the space I4 into the space 20. Gas emerging from the orifice 2i aspirates air through the openings, 22 forming a combustible mixture after the manner of a Bunsen burner. It is to be noted that if the fit between the sleeve I8 and the plug 19 is such that gas leaks along it this gas is drawn in with the air entering the slots 22 and does not escape.

The combustible mixture as described enters the tube 23 which is made of a materialwhich is resistant to relatively high temperature and also has a relatively high temperature coefiiclent of expansion so that upon heating it lengthens and upon cooling it shortens by an amount greater than that necessary to take up the space between the valve I2 and the stop I3 when the valve is closed. The tube 23 has drilled in it numerous small holes 24 (Fig. 6) through which gas may emerge and burn close to the surface of the tube thereby heating it to a relatively high degree and causing the valve I2 to open if it is not already open and to cause the above referred to frictional engagement to yield when the valve I2 is opened an amount pre-determined by the adjustment of the stop I3.

Referring now to Fig. 6, the tube 23 is rigidly attached at 25 to the cross member 26 to which,

in turn, are attached the members 21, of which there may be any desired number. The members 21 are preferably made of material having the same temperature coefficient of expansion as the tube 23. The members 21 are in turn attached at their opposite ends to the body 23 of the safety pilot.

It is now clear that lengthening of the tube 23, as by heating,.tends to open the valve I2 to an extent determined by the adjustment of the stop I3 and upon further lengthening of the tube 23 the frictional engagement between the prongs I1 and the sleeve I8 will yield. Shortening of the tube 23, as by cooling will result in an immediate tendency towards closure of the valve I2, in fact, the valve may be closed when the tube 23 is longer than was required for full opening of the valve I2 while the tube was lengthening due, for example, to an initial rise in temperature.

Referring to Figs. 9 and 11 it will be noted that gas in the space I4 may pass to the chamber 23 and may also pass into the opening 23. The opening 29 leads to the conduit 33 which is connected to the three-way valve 3| the function of which will be described later but which normally only furnishes a continuation of the conduit 30. The conduit 33 leads to a valve shown generally at 32 as a liquid expansion thermostatic valve and arranged so that, upon suflicient temperature rise of any part of its temperature sensitive system gas, is prevented from passing from the conduit 33 to the conduit 33. It is evident that the valve member 32 may occupy any intermediate position between closed and effectively wide open and in any of these positions the gas pressure in the conduit 33 will vary with the degree of opening of the valve member 32 provided there are means for some escape of gas from the conduit 33.

The temperature sensitive portion of the thermostatic valve 32 is, for convenience, shown with a relatively large bulb sensitive, for example, to room temperature at 34, and a much smaller bulb 35 located in the mixing chamber of the Bunsen burner.

Gas under pressure in the conduit 33 may pass to the T connection 36 and at all times from the connection 33 through the conduit 31 to the space 33 of the bleed gas burner section of the safety pilot as shown in Fig. 11. The space'33 is vented by the tubular member 33 having the orifice 43 arranged, with the openings 4| to operate as a Bunsen burner and produce a combustible mixture to be burned at the outlet 42 and slits 43 of the tube 44. The tube 44 is arranged so that gas issuing from the opening 42 and slits 43 is ignited by gas burning at the openings 24.

Referring now to Figs. 2 and 11, it will be noted that the second discharge branch 45 of the T connection 3B is vented by means of the orifice 43 into the space 41 from which the only egress is through the opening 43 which normally connects the space 41 with the space 43. Gas in the space 43 may pass through the opening 53 to the conduit 5i and thus into the annular space 52 (Fig. 7) of the bleed gas burner. Gas escaping under pressure through the orifice 43 aspirates air through the openings H, as previously described, to form a combustible mixture. Gas passing through the annular space 52, which surrounds the tube 39 (as may best be seen in Fig, 7), is therefore intimately mixed with the-foregoing described combustible mixture and burned with it at the outlets 42 and 43.

Referring to Fig. 2, the partition 33, in which is the opening 43, separates the spaces 41 and 43. If the opening 43 is closed, as by the diaphragm 35 pressure difference may be set up between the spaces 41 and 43. Under conditions to be described later it is desirable to limit this pressure difference and for this purpose a relief valve, as shown in Fig. 4, is provided. As shown in Fig. 4, the disc 31, thick at the periphery has a lapped fit against the partition 33 and is located by the stem 53. The opening 53 permits pressure in the space 41 to be exerted against the relatively large area of the disc 31 which is held against the pressure by the adjustable spring 30. At a pressure in the space 41, pre-determined by the adjustment of the spring 30, the disc 31 is lifted sufficiently to permit escape of gas from the space 41 into the space 43, thus limiting the pressure in the space 41. It will be seen that this action limits the pressure which may be supplied to the burner 3. A very slight lifting of the disc 51 is sufficient to limit the rise of pressure in the space 41 since the supply of gas to it is limited by the orifice 43 (Fig. 2).

Referring now to Figs. 2 and 11, pressure in the space 41 is exerted against the diaphragm 3| tending to move it to the position indicated by the dotted line 3i thus engaging the stem of the valve 3 and tending to move it to the position I thereby permitting flow of gas into the space I, the conduit 1, and thus to the burner I. It will be noted that themain valve outlet pressure will have a value which will be proportional to the position of the condition responsive controller I2 within an upper limit defined by the adjustment of spring Bl (Fig. 4) and a lower limit defined by the adjustment of-spring N (Fig. 2). Thus, with valve I open. in the event of an Increase in supply pressure at I, the pressure in the space 6 will increase and, because of opening 62, the pressure in space II will increase, moving valve I toward closed position. This movement of valve I toward closed position reduces the pressure in space 8, thereby tending to return the pressure on the burner side of valve I back to its original value. Upon a reduction in pressure at I, valve I will open slightly. r ucing the pressure drop across valve I thereby tending to return the pressure on the burner side of valve I to its original value. Upon either a supply Dressure increase or decrease at I, it will be understood that such pressure variation will also be reflected in space 41, and in a static system this pressure increment would Just balance the additional pressure increment in chamber II resulting from the pressure variation at I, thus valve I would have no pressure regulating eil'ect. However, in the system disclosed, the gas passage defined by pipe I0, valve I2, pipe 30, valve II and pipe 33 is not a static system, see flows therethrough when the burner I is operating. and the consequent energy losses through friction in the pipes III, II and II and the losses at the restrictions I2 and 48 will reduce the additional pressure increment which appears in space 41 as a result of a supply pressure variation at I. Since the pressurechange in the space 6 caused by a variation in supply pressure at I will not, therefore, be balanced the resulting pressure change in space 41 because of the frictional and restriction losses the valve 3 will be moved to compensate for any variation in supply pressure at I, although such pressure regulation by valve I will not be entirely complete because of the small pressure change which appears in space 41 as a result of such supply pressure variation.

Because the pressure regulation by valve I is somewhat incomplete, as pointed out above, a supply pressure increase at I will result in increased pressure in space 6 and pipe 1 (although the magnitude of this pressure increase will be less than the increase in supply pressure because of the regulating effect of valve I pointed out in the preceding paragraph). In order to limit the pressure increase in the space I and pipe I, brought about by an increase in supply pressure at I, a relief valve'formed by opening BI and disc 51 is provided as previously described. Thus upon a relatively large increase in supply pressure at I, the pressure of gas flowing to burner 8 will increase, the pressure in space 41 will also increase (though by a proportionally smaller amount) and when the pressure in space 41 reaches a value depending on the setting of the relief valve biasing spring ill. the disc II will be raised slightly allowing gas to escape through opening 59 and bleed opening 50 thereby relieving the pressure in space 41 and allowing valve 3 to move toward closed position an amount suilicient to limit the pressure in the space 8 to the desired maximum value. It willthus be apparent that the valve formed by opening II and disc 5! acts as a relief valve and the adiustment 6 of spring I reestablishes a maximum, limiting value for the pressure of the gas supplied to burner I.

The diaphragm II is moved to the position II and the pressure in the space I! becomes equal to the pressure in the space It since these two spaces are connected by the orifice II and the passage II but while 4| is open substantially zero pressure exists in the space 41. The adjustable spring 84 is provided so that any desired pressure in the space Il may be required to cause the diaphragm II to close the opening II. It is apparent that whenever pressure in the space It becomes less than this value the opening II will again be opened and pressure in the space II will immediatelyfall-to substantially zero and arranged so that when the opening II is closed the valve I will close.

mentioned above,

Referring now to Fig. 11, the operation of the three-way valve II, above referred to, may now be described. It the valve I2, is closed the pilot burner cannot be lighted unless auxiliary means are provided. Valve II normally nly provides continuity for conduit III but if th valve II is closed and it is desired to light the pilot, the valve II may be turned to the position indicated at II. It is now seen that gas may pass from the conduit III to the space II and be lighted, but while the valve II is in the sition II no valve 32 and II the valve I2 is opened and the 3-way valve may be turned from the position II to the position II- and gas will continue'to tlzie pilot burner and also to the control valve atures of the tube rapid closing of the valve I2, with immediately subsequent slipping of the frictional engagement between the prongs I1 and member I8 (Fig. 9). In normal operation gas passing to the valve I2 is throttled in proportion to the amount of opening of valve element 32' so that, normally, the pressure in conduit II is less than that in conduit 30, provided that conduit 33 is not closed but has at least a small discharge opening.

Gas can escape at all times from the conduit II through conduit 31 and orifice 40 so that pressure in the space 54 is at a value which depends on the demand for heat at the valve 32. If the opening 48 is not closed by the diaphragm II, in the position 55' (Fig. 2), then gas may pass through the orifice 46, through opening 48. to the conduit SI, and to the bleed gas burner tube 44, as described. Under these conditions the pressure in the space 41 is negligible, the valve 3 is closed and the pressure in conduit therefore in the space 54, is less than be if the opening is were closed.

With an increasing demand for heat at the valve 32 pressure in space It rises but pressure in space 41 does not since it is vented by a low restriction opening 50. At a pressure pre-determined by the adjustment of spring 64 the opening 48 is closed and pressure in the space 41 II, and it would the pilot may be supplied to builds up suddenly to equal that in the conduit 33 which, in turn, rises suddenly because no gas is escaping through the orifice 48 except sufllcient to built up pressure in space 41. It is now seen that at a pre-determined pressure in conduit 33 the valve 3 is opened suddenly and supplies pressure to the burner 8 at a value which is determined by the tension of spring 84, spring 4, and the ratio of the flow restrictions of the valve 32' and the orifices 40 and 48. If the restriction of the orifice 48 is large compared with that of orifice 48 pressure in the space 84 will not build up greatly when the opening 48 is closed, in fact desired results as to initial and final burner pressures over a wide range may be obtained by suitable variations of all of these flow restrictions since, as above described, pressure applied to the burner 8 is proportional to the pressure in space 41. It will be noted that because of the rapid increase in pressure in space 41, the initial movement of valve 8 in opening direction is relatively rapid, but as valve 3 opens progressively wider the increasing pressure in space 83 acting on diaphragm 8| tends to retard this movement, the final position of valve 3 being fixed at the point where the pressure drop across valve 3 is sufilcient to hold the pressure in space 83 to a value less than the pressure in space 41 by an amount depending on the adjustment of spring 4. The pressure in space 8, therefore, is always proportional to the pressure in the space 41, but less, depending on the effort exerted by spring 4 which acts to close the valve when the pressure in space 41 drops to a predetermined minimum value, and thus to completely shut oil gas supply to the burner 8 when little or no gas is being passed through valve 32'.

As demand for heat at the valve 32 decreases pressure in the spaces 84 and 41 decreases proportionately and therefore also the pressure supplied to the burner 8. As the pressure in the space 84 becomes less than that at which the diaphragm 88 closed the opening 48, while the pressure was rising, the diaphragm 88 opens the opening 48, permitting a sudden drop to practically zero pressure in the space 41. The valve 3 therefore closes suddenly. It is to be noted that the pressure to the burner immediately prior to shut-oil is substantially less than that which was supplied when the valve 3 opened. The burner is therefore supplied with a relatively high lighting pressure and low cut-off pressure and, during operation, with a pressure which is proportional to the demand for heat.

It will now be apparent that theprincipal function of the passage 48 and diaphragm 88 is to provide the initial, quick opening of valve 3. Thus when passage 48 is open the pressure of gas passed by valve 32 is held at a low value since such gas is bled through two bleed openings (conduits 31 and 81) in parallel. As soon as passage 48 is closed one of these bleeds (conduit 81) is suddenly cut oil and the pressure in conduit 33 and consequently in space 41 therefore increases suddenly, moving valve 3 rapidly in valve-opening direction. In the closing operation, when passage 48 is opened, the availability of an additional bleed (opening 88 and conduit 8|) rapidly reduces the pressure above diaphragm 41 and valve 3 closes rapidly. Without passage 48 and diaphragm 88, as valve 32' moved slowly in opening direction, valve 3 would also move slowly in opening direction, and gas would be initially supplied to burner 8 at a pressurebelow a satisfactory lighting pressure, producing an eminently unsatisfactory igniting condition at Bunsen type burner I as previously pointed out. Additionally, upon a decrease in pressure above diaphragm 88, when the predetermined low pressure (determined by the adjustment of spring 84) is reached, the passage 48 is opened, the pressure in space 41 decreases suddenly and the pressure supplied to the niain burner decreases suddenly because of the sudden closure of main valve 3. 1

As previously described, flashbacks are apt to occur in the operation of a Bunsen burner. When this occurs intense heat is generated in the mixing chamber of the burner. In this embodiment of my invention I show a small portion 38, of the thermosensit-ive system of the valve 32 inserted in the burner mixer. Should a flashback occur the bulb 38 is immediately and intensely heated, resulting in sudden cutting oil of the gas supply to the burner 8 and consequent extinguishment of the flashback. When the bulb 38 has cooled, which it will do rapidly, gas will again be supplied to the burner as described. If no flashback occurs again normal operation will take place but the operation will be repeated as often as flashbacks occur. It is to be noted that flashbacks are much more apt to occur with modulated pressure operation than with ordinary full pressure on and off operation.

With raw gas, or radiant type or burners flashbacks cannot occur and therefore an equivalent of bulb 35, Fig. 11, is not shown in Fig. 1.

In many cases a single burner is not sufllcient to meet the heat requirements and it is desired to operate additional burners to supply high rate demand, but to operate the additional burners only when they are required so that the burners which are in operation may operate a higher percentage of the time at relatively high rates and therefore at higher eiiiciency. Fig. 12 shows a manner in which this may be done.

In Fig. 12 the controller 32", regulating valve 2' (which is identical with the valve shown in Fig. 2), safety pilot 8, three-way valve 3i", and burner 8' are arranged in the same manner as the corresponding devices in Fig. 11, with the addition of the conduit 33 leading pressure in conduit 1 to the adjustable restriction 18 which is connected by conduit means to an additional regulating valve 2" (which is identical with the valve 2') in the same manner as conduit 33 in Fig. 11. It is now clear that the pressure being supplied to the burner 8' serves to actuate the valve 2" and therefore to deliver gas to the burner 8" in the same manner as the valve 2' delivers gas to the burner 8' except as modified by adjustment of the adjustable restriction 18 and the springs corresponding to the springs 84 and 4 of Fig. 2, and that many burners may be operated in the same manner under the command of a single controller. The manner in which these adjustments must be made in order to obtain desired results will be apparent to those skilled in the art.

I claim-as my invention:

1. In a control system of the type wherein the condition controller is actuated by a fluid pressure motor, the regulating movement of the controller being proportional to the fluid pressure supplied to said fluid pressure motor: means for producing variable controlling pressure comprising a fluid pressure source for supplying substantially constant fluid pressure to a variable flow restriction; a first conduit for conducting outflow of said variable flow restriction to a first filed closed position when pressure 9 orifice, said orifice discharging to atmospheric pressure; a second conduit also conducting outflow of said variable flow restriction to a second fixed orifice, said second orifice discharging into a fluid pressure motor, said motor having an opening to atmospheric pressure; valve means for duit, and when pressure in said first conduit be-' comes less than a predetermined value said valve is opened and pressure supplied to said fluid pressure motor becomes substantially'atmospheric.

2. In a burner control system: a burner; a t

conduit connecting said burner to asource of fluid fuel; a main throttling valve in said conduit for controlling fluid flow therethrough and biased toward a closed position; a motor for operating said valve comprising means forming a first and a second chamber separated by a diaphragm; means operatively connecting said diaphragm to said valve; means for continuously subjecting said second chamber to the outlet pressure of the valve so as to modify the operation of the motor in accordance with that pressure; said diaphragm permitting said valve to move to in said first chamber is substantially atmospheric; means defining a third chamber vented to atmospheric pressure and having a fluid passage connecting it to-said first chamber; means for controlling fiow through said passage comprising an additional valve, biased toward an open position; motor means for operating said additional valve comprising an additional diaphragm forming a wall of said third chamber, and means defining with said additional diaphragm a fourth pressure chamber at the side of the diaphragm opposite the third chamber, said fourth chamber being. connected by conduit means including a fixed orifice, to said first chamber so that fluid pressure in safd fourth chamber and said first chamber may be unequal when said additional valve is open, and substantially equal when said additional valve is closed, the pressure in said first chamber being substantially atmospheric with no fuel supplied to said burner when the fluid said fourth chamber is less than a predetermined value; the pressure in said first chamber being greater than atmospheric when fluid pressure supplied to said fourth chamber exceeds a predetermined value whereby fuel is supplied to said burner in proportion to said last named fluid pressure.

3. Apparatus for use in a control system of the type having a main burner, a pilot burner and control means responsive to a condition resulting from the operation of said main burner for controlling the flow of fuel to the main burner, said apparatus comprising: a main valve, a motor for operating said valve including means defining a first and second chamber separated by a movable partition, means operatively cnnesting said partition to said main valve, means for introducing a fluid at a control pressure into said first chamber, including a control fluid conduit with an orifice bleed to atmospheric pressure pressure supplied to a of fuel to a second main burner,

at one of its ends, a throttling valve in said control fluid conduit operated by said control means. a safety pilot burner valve in said control fiuld conduit operative to close said control fluid conduit when said pilot burner is extinguished. means for venting said first chamber including an opening therein, means for closing said opening when said control pressure attains a predetermined value, and means for subjecting said second chamber to the outlet pressure of said main valve for causing said main valve to remain closed until said control pressure reaches said predetermined value and thereupon moves rapidly in valve opening direction.

4. In a multiple burner control system. a first main valve for controlling the flow of fuel to a first main burner, a first fluid motor for operating said first main valve, a control fluid conduit.

having an adjustable flow restriction therein for introducing a control pressure into said first fluid motor, a second main valve for controlling the flow a second fluid motor for operating said second main valve means for introducing a control pressure into said second fluid motor including a fluid conduit connecting the outlet side of said first main. valve with said second fiuid motor whereby pressure of fuel available at saidsecond main burner varies able partition;

proportionally with the pressure of fuel available at said first main burner.

5. In a burner control system: a burner, a conduit connecting saidv burner to a source of fluid fuel; a throttling valve in said conduit for controlling fluid flow therethrough and biased toward a closed position; a motor for operating said valve comprising means defining a first and a second pressure chamber separated by a movmeans operatively connecting said partition to said valve; means for passing controlling pressure fluid to said first chamber; means responsive to a, condition resulting from the operation of the burner for varying pressure in said first chamber in accordance with the magnitude of said condition, a passage in said] first chamber venting it to atmospheric pressure, a closure for said passage movable between efiective and ineffective positions for sealing said first chamber against atmospheric pressure when in effective position, means for moving said last named valve between said efl'ective and inefi'ective positions in response and means for continuously subjecting said. second chamber to the outlet pressure of the valve so as to modify the operation of said motor in accordance with that pressure, whereby the rate of delivery of fiuid fuel to said burner is proportional to the magnitude of said condition.

6. In a burner control system: a burner, a conduit connecting said burner to a source of fluid fuel; a throttling valve in said conduit for controlling fluid flow therethrough and biased toward a closed position; a motor for operating said valve comprising means defining a first and a second pressure chamber separated by a movable partition; means operatively connecting said partition to said valve; means for passing controlling pressure fluid to said first chamber: means responsive to a condition resulting from the operation of the burner for varying pressure in said first chamber in accordance with the magnitude of said condition, a passage in said first chamber venting it to atmospheric pressure, a closure for said passage movable between efi'ective and ineffective positions for sealing said first chamber against atmospheric pressure when in to said varying pressure. p

11 effective position, means for moving said last named valve between said effective and inefiective positions in response to said varying pressure comprising an additional motor having a passage thereto for introducing said varying pressure therein and-having adjustable resilient means for biasing said closure toward ineffective position, and means for continuously subjecting said second chamber to the outlet pressure of the valve so as to modify the operation of said first named motor in accordance with that pressure, whereby the rate of delivery of fluid fuel to said burner is proportional to the magnitude of said condition.

LEWIS L. CUNNINGHAM.

' 12 REFERENCES CITED The tollowing references are of record in the tile of this patent:

UNITED STATES PATENTS Number v Name Date 2,185,364 Andrews Jan. 2, 1940 2,207,941 Otto July 16, 1940 2,244,555 Harris June 3, 1941 2,293,314 Spence Aug. 18, 1942 2,333,775 Gille Nov. 9, 1943 FOREIGN PATENTS Number Country Date Switzerland Sept. 16, 1935 

